Music is a beautiful sound and almost all people enjoy listening to music. There are different types of music, including, for example, classical music, pop music, etc., and people usually have their own choice of favored music types. Most young students prefer to pop music and often enjoy listening to the music either indoors or outdoors. The development of portable stereophonic reproducing products, such as the so-called walkman, enable people to carry the stereophonic products with them and listen to the music with earphones without disturbing other surrounding people. It is really a wonderful feeling to freely enjoy music at any time and at any place.
However, to listen to music or broadcast using earphones for a prolonged time tends to endanger or be detrimental to the listener's eardrums and adversely affect the listener's normal hearing ability. Moreover, it is uncomfortable after the earphones have been plugged in the ear for an extended time period. Another disadvantage of the walkman is it is designed for one user to listen to the music alone, and it is impossible for a group of companions to enjoy the music at the same time via a walkman because the latter could not play the sound loudly.